Gas turbine engines are frequently used to power helicopters, as well as various other vehicles and other devices. In helicopters, under ordinary flying conditions, fuel flow to the engine is typically controlled by an automatic fuel flow control system. The automatic fuel flow control system can be used to provide optimal fuel flow to the engine by automatically adjusting fuel flow based, for example, on measured values of various engine and helicopter operating conditions.
Helicopters with automatic engine control units are normally equipped with a manual mode system as backup to the automatic system should the automatic system fail. This manual mode allows the pilot direct manual control over engine fuel flow in order to maintain engine power and achieve a save landing. Helicopter pilots will also, as part of regular training exercises, wish to manually control engine fuel flow, in order to practice this very difficult situation where automatic control of the engine has been lost. However, while the pilot is flying the helicopter in the manual training mode, typically fuel flow to the engine is controlled exclusively, or almost exclusively, by the helicopter pilot, without the benefit of various features of the automatic fuel flow control system, such as automatic engine fuel flow adjustment based on values of various engine operating conditions.
Accordingly, there is a need for a system, device, or method for allowing manual control of fuel flow to a gas turbine engine during training, while retaining features of an automatic fuel flow control system available to the pilot should the pilot inadvertently cause an unsafe flight condition for either engine or helicopter to occur during this training. The present invention addresses at least this need.